Retirement benefits - Net pension (benefit) expense (Details) - Pension Plans - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
U.S. Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 6,972	$ 7,326	$ 20,918	$ 21,977
Interest cost	46,013	47,376	138,039	142,128
Expected return on plan assets	(61,243)	(64,383)	(183,730)	(193,148)
Amortization of prior service cost	762	227	2,287	681
Amortization of net actuarial loss	2,577	401	7,732	1,204
Net pension (benefit) expense	(4,919)	(9,053)	(14,754)	(27,158)
Non-U.S. Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	5,378	5,320	16,459	16,616
Interest cost	18,461	20,268	56,267	59,949
Expected return on plan assets	(21,084)	(23,998)	(64,263)	(71,714)
Amortization of prior service cost	63	92	191	274
Amortization of net actuarial loss	1,604	1,591	4,890	4,763
Net pension (benefit) expense	$ 4,422	$ 3,273	$ 13,544	$ 9,888